在此論文中我們介紹了裝有RF電漿輔助氮氣源的Veeco Applied EPI 930分子束磊晶系統，以及利用此系統成長寬能隙半導體氮化鎵的過程與一些檢驗樣品的測量方法。我們討論了關於成長過程中不同成長參數對氮化鎵磊晶層的影響，包括藍寶石基板的氮化處理、低溫氮化鎵緩衝層與氮化鎵磊晶層等。藍寶石基板的氮化處理對獲得高品質的樣品是必須的，而成長在經過良好氮化處理的藍寶石基板上的樣品有較好的結晶性，其x-ray繞射曲線之半高寬比長在未經氮化處理之基板上之樣品要小了一個數量級。對於長在未經氮化處理的基板上之低溫氮化鎵緩衝層而言，其成長溫度是最重要的參數，成長溫度較高時會有較好的結晶性，此外，較薄、成長速率較慢與較低的氮/鎵比會得到較好的樣品。在研究氮化鎵磊晶層之氮/鎵比時發現，偏於Ga-rich的樣品其光致螢光光譜的半高寬較小，且表面較為平整；在比例接近相等時會有最少的載子濃度與最窄的對稱x-ray繞射曲線；如果是偏於N-rich時會有較高的載子移動率與較少的缺陷。在以SdH對有機金屬氣相沈積法成長樣品的實驗中，觀察到兩種兩個頻率拍頻的情形。一個是在Alx-δInδGa1-xN/GaN (δ< 0.01 %)異質結構中，因為含有少量體積較大的銦原子減小不同磊晶層間的應力，介面上之壓電場效應變小，造成第二次能階與第一次能階的能隙縮短，所以看到了兩個頻率拍頻的情形。另一個是在AlxGa1-xN/GaN (x= 0.25) 異質結構中，因inversion-asymmetry-induced bulk k3 term引起的有限零磁場下之自旋分裂所產生的。

Veeco Applied EPI 930 molecular beam epitaxy system equipped with a radio frequency plasma assisted nitrogen source has been introduced and the growth procedure and some specialized measurements are also described. The GaN thin films grown by RF-MBE have been talked about nitridation, low temperature GaN buffer layer, and GaN epilayer. The nitridation is a necessary for grown GaN on c-sapphire. From the result of the HRXRD symmetric (002) rocking curve, the magnitude of the FWHM of the GaN films without nitridation was larger than the films with nitridation. The growth temperature of the LT GaN buffer layer was the major factor on the quality of GaN epilayer which grown on the almost without nitridated sapphire substrate. The growth condition of high growth temperature, thin, low growth rate, and low N/Ga ratio of the LT GaN buffer layer can improve the sequent GaN epilayer quality. On the other hand, in the N/Ga flux ratio of GaN epitaxy layer experiment, we have found three interesting results. First, the narrowest peak width of PL spectrum appeared in a slight Ga-rich condition. Second, the smallest of HRXRD FWHM appeared in the nearly stoichiometry condition. Third, the highest electron mobility and less overall dislocations appeared in a slight N-rich condition. Finally, we report the results about AlGaN/GaN heterostructure grown by metalorganic chemical vapor deposition. The piezoelectric effect on the Alx-δInδGa1-xN/GaN heterostructures was investigated and we found that a little In atom in the spacer (δ< 0.01 %) will substantially reduce the strain at interface due to the much larger size of the In atom in comparison to Al and Ga atoms. The electric field at the interface is reduced one order of magnitude smaller than that of the heterostructure without In atom. Two SdH oscillations beat each other due to the population of the lowest two subbands was been seen. Another two SdH oscillations beating have been observed in modulation-doped AlxGa1-xN/GaN heterostructures caused by the finite zero-filed spin splitting due to the inversion-asymmetry-induced bulk k3 term.

Abstract i
摘要 iii
Chapter 1 Introduction 1
Chapter 2 Plasma assisted MBE system and
experimental procedure 8
2.1 Radio frequency plasma assisted
molecular beam epitaxial system 8
2.1.1 Chamber 9
2.1.2 Sample manipulation 9
2.1.3 Knudsen cells 11
2.1.4 RF plasma assisted nitrogen source 11
2.1.5 RHEED 14
2.2 Growth procedures 15
2.2.1 Substrate preparation 15
2.2.2 Nitridation 17
2.2.3 Buffer layer 18
2.2.4 GaN epitaxial layer 19
2.3 Characteristic Measurements 19
2.3.1 Reflective high energy electron diffraction 19
2.3.2 Alpha step surface profiler 20
2.3.3 Field emission scanning electron microscopy 21
2.3.4 Transmission electron microscope 21
2.3.5 Atomic force microscope 22
2.3.6 Photoluminescence 22
2.3.7 Raman scattering 23
2.3.8 High resolution X-ray diffraction 24
2.3.9 Auger electron spectroscopy 24
2.3.10 Secondary ion mass spectrometry 25
2.3.11 Electron probe microanalyzer 25
2.3.12 Hall effect measurement 26
2.3.13 Shubnikov-de Haas effect and quantum Hall effect 26
References 28
Figures 29
Chapter 3 Results of undoped GaN thin films 42
3.1 Nitridation 43
3.2 Low temperature GaN buffer layer
growth 50
3.2.1 Growth temperature 52
3.3.2 Thickness 56
3.2.3 Growth rate 57
3.2.4 N/Ga ratio 58
3.3 GaN epitaxy layer growth 60
References 68
Figures 71
Chapter 4 Results of AlGaN/GaN
heterostructures 100
4.1 Piezoelectric effect on
Al0.35-δInδGa0.65N/GaN heterostructures 101
4.2 Spin splitting in modulation-doped
AlxGa1–xN/GaN heterostructures 107
References 115
Figures 117
Chapter 5 Conclusions 133
Chapter 6 Work in the future 136
References 140
Figures 142
Publication List 143

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